Advisory (ICSA-12-258-01)

IOServer OPC Server Multiple Vulnerabilities

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Overview

Independent researcher Hinge of foofus.net has identified multiple vulnerabilities1 in IOServer’s OPC Server application. IOServer has released a new version of the product that partially mitigates these vulnerabilities. Hinge has tested the new version and found that it partially resolves these vulnerabilities. These vulnerabilities can be exploited remotely. Exploits that target these vulnerabilities are known to be publicly available.

Affected Products

The following IOServer OPC Server versions are affected:

IOServer OPC Server 1.0.18.0 and earlier.

Impact

These vulnerabilities allow an attacker to download any file on the file system without authentication.

Impact to individual organizations depends on many factors that are unique to each organization. ICS-CERT recommends that organizations evaluate the impact of these vulnerabilities based on their operational environment, architecture, and product implementation.

Background

IOServer is an Australia-based company that produces the affected product, OPC Server, which is designed to exchange data between the human-machine interface and the programmable logic controllers. According to IOServer, OPC Server is deployed across several sectors including manufacturing, building automation, oil and gas, and electric utilities. IOServer estimates that these products are used primarily in the United States and Europe with a small percentage in Asia.

Vulnerability Characterization

Vulnerability Overview

CVE-2012-46802 has been assigned to these three closely related vulnerabilities. A CVSS v2 base score of 7.8 has been assigned; the CVSS vector string is (AV:N/AC:L/Au:N/C:C/I:N/A:N).

The software uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory. However, the software does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. This allows arbitrary access to any file on the server.

Vulnerability Details

Exploitability

These vulnerabilities could be exploited remotely.

Existence of Exploit

Exploits that target these vulnerabilities are publicly available.

Difficulty

An attacker with a low skill would be able to exploit these vulnerabilities.

Mitigation

IOServer has created a new version (Version 1.0.19.06) to correct the directory traversal vulnerability (Vulnerability #3 above). The researcher has found that this new version still contains insufficient access controls (Vulnerability #1) and allows directory listings (Vulnerability #2) inside the root directory and its subdirectories.

In addition to the patch, the researcher recommends that users ensure that the “Root Directory” configuration value has a trailing backslash. This helps to mitigate the remaining issues, although an attacker can still get a directory listing of the root directory itself (but not subdirectories) with this in place.

ICS-CERT encourages asset owners to take additional defensive measures to protect against this and other cybersecurity risks.

Minimize network exposure for all control system devices. Critical devices should not directly face the Internet.

Locate control system networks and remote devices behind firewalls, and isolate them from the business network.

When remote access is required, use secure methods, such as Virtual Private Networks (VPNs), recognizing that VPN is only as secure as the connected devices.

The Control Systems Security Program (CSSP) also provides a section for control systems security recommended practices on the CSSP web page. Several recommended practices are available for reading and download, including Improving Industrial Control Systems Cybersecurity with Defense-in-Depth Strategies. ICS-CERT reminds organizations to perform proper impact analysis and risk assessment prior to taking defensive measures.

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Join the Secure Portal

ICS-CERT encourages U.S. asset owners and operators to join the Control Systems compartment of the US-CERT secure portal. Send your name, e-mail address, and company affiliation to ics-cert@hq.dhs.gov.